Explicit treatment of the gallium 3delectrons in GaN using the plane-wave pseudopotential method

The plane-wave pseudopotential (PWPP) method has been used to calculate structural and electronic properties of wurtzite and zinc-blende GaN. In contrast to previous studies using the PWPP method, the gallium 3d electrons were treated as valence electrons. This yields larger lattice constants and smaller energy gaps as compared with previous PWPP results. For wurtzite, the three structural parameters were found to be a=3.162 Å, c=5.142 Å, and u=0.377. For zinc blende, the cubic lattice constant was found to be ${\mathit{a}}_0$=4.460 Å. The lattice constants are about 1% smaller than measured values and the cubic lattice constant is within about 0.2% of results from full-potential all-electron calculations. This study demonstrates that it is both possible and practical to treat gallium 3d electrons explicitly using the PWPP method.